Fuse plug



Feb.` 9, 1932. T, B, BURN@ 1,844,030

FUSE PLUG Filed April 25, 1930 Patented Feb. 9, '1932 UNITED STATES PATENT OFFICE FUSE 'PLUG Application led April 25, 1930. Serial No. 447,393.

My present invention relates to improvements in fuse plugs for electrical circuits, as for electric lamps, and especially to an emergency signal for indicating the burning out of a fuse 'in the fuse plug. The fuse plugs of In invention are adapted for use in the usua fuse sockets in cut-out or fuse-plug boxes, ordinarily found upon the basement Wall of a house, or other building that is Wired for electric lighting. Y

' As is well known, when a fuse blows out and the lamps of a circuit are extinguished, the ordinary householder has difficulty in ascertaining which one of several fuse plugs in l5 the cut-out box has burned its fuse.

In carrying out my invention I substitute for the usual fuse plu s a set of plugs involving my invention, an each of the lmproved plugs includes an incandescent lamp or signal, which lamp is normally extinguished. :When the fuse of any oneof the plugs burns out from any cause, the lamp of the burned out plug is automatically illuminated, thus indicating to the observer which plug requires 33' a fresh fuse.

' The plugs are equipped with means for replacing and renewing the fuses, and such fuses or fuse-links may with facility and convenience be substituted for the burned fuselinks.

The invent-ion consists in certain novel combinations and arrangements of parts as will hereinafter be more fully set forth and claimed.

In the accompanying drawings I have illustrated one com lete example of the physical embodiment o my invention wherein the parts are combined and arranged according to one mode I have thus far devised for the practical application of the principles of my invention, but it will be understood that changes and alterations may be made in the exemplified structure within the scope of my claims Without departing from the principles of my invention.

Figure 1 is a view of a signaling fuse plug embodying my invention, part ofthe covering being shown in section. Figure 2 is a view o from the opposite side of Figure 1, with the lamp bulb omitted.

Figure 3 is an enlarged detail sectional View through the body of the plug, omitting the lamp, and showing the removable fuse member in elevation. 1

Figure 4 is a detail sectional View of the flllse member removed from the body of the p ug.

Figure 5 is a section at line 5-5 of Figure 4. A

In carrying out my invention I employ a standard, small size incandescent lamp l having the usual screw head 2 which threads into the complementary shell 3 of the body of the plug. The body of the plug, as here shown comprises three sections 4, 5, and 6, of suitable material such as porcelain, and these sections are recessed, grooved, and slotted as usual for the accommodation of the conducttrs and other electricalv elements of the fuse p ug.

r1"he sections are fastened together by means of bolts or screws 7 and 8, and clamped with nuts 9 on the threaded ends of the screws as indicated in the drawings.

The plug is fashioned with a threaded head 10 that screws into the usual socket provided to receive the fuse plug.

In the preferred form of my invention I utilize a removable fuse holder which includes a post 11 of suitable insulating material that 1s fashioned with a pair o'f diametrically arranged wings 12, and a contact head 13 is carried at one end of the post for contact with a complementary contact member in y the socket to which the fuse plug is attached.

This contact head is formed integral with a tubular stem 14 that is rigidly carriedin the post, and a slide bolt 15 is enclosed in the stem and is fashioned with a contact head 16 at the end of the holder opposite to the head 13.

IVithin the tubular stem, and interposed between the head 13 and the inner end of the slide bolt, I locate a spring 17 that' has a tendency to urge the headed bolt from the tubular stem.

The holder-post 11 has secured thereto an inset, fixed metallic ring 18 having a tapered annular flange 18', and this flange 1S is employed in holding the fuse link 19. The fuse link is a thin strip of suitable material that is weakened by cutting out its edges as 19', and the link is readily burned out and severed when the load becomes sulliciently heavy, as to blow the fuse.

The fuse link is retained on the holder, at

one end, by a clamp ring 20 having a pair of clamp anges 20a, one of which langes coacts with the tapered flange 18 of the Xed ring 18. At its other end the fuse link is retained by a cap 21 fitted over the head 16 ot' the slide boltf15. In applying the fuse link, the holder is first removed from the plug, the cap 21 is removed from the head 16 and the clamp ring 20 is loosened around the fixed ring 18. One end of the link is th'en clamped between the tapered rings 18 and 20. The slide bolt is then retracted or pushed within its stem against the tension of -the sprinv, the end of the flink is laid against the side of thehead andithe'cap is then fitted over the end of the link and the head.' Both ends of the link are held frictionally by the clamping members, to withstand the tension of the compressed' spring 17, and the spring and link hold the slide bolt in its retracted position in the tubular stem. If and when the fuse is severed, as by a blow, the spring is free to project the slide bolt and its head closes a lampcircuit as will be described.

The "detachable clamp ring v2() is slotted at 22 to accommodate the wings 12 of the holder, and these wings hold the ring against turning and guide it as it is slid into or out of engagement with one end of the fuse link.

` The holder is inserted in the hollow body section 6 of the plug, the two wings frictionally engaging in grooves within the section,

and a resilient leaf .23 rigid with or integral. with the shell 10 occupies one of these grooves for frictional engagement with the holder,

vso that the latter is frictionally retained within the hollow section, with the contact head 13 exterior of the plug.

lVithin the hollow section 6 a stationary contact head 24 is located, against which the capped head 16 impinges when the fuse link is severed and the spring 17 projects the slide bolt and contact head.

Before the fuse link is severed, or burned out, the current from the plug socket (not shown) passes through the head 13, stem 14, and head 16 to the. link 19, thence by way of rings 18 and 20 to the shell 10 of the plug and to the shell of the socket in the head shell 10 is screwed, and from there the usual con# nections or wiring is made to the source of electrical supply.

When the capped head 16 frictionally engages the stationary head 24, the lamp 1 is illumined, thus giving a warning or signal that the plug of lamp l is the fuse plug that has burned out, in order that a fresh fuse link may be applied to the holder after the severed ends have been removed.

Tothe stationary head 24 a wire 25 is attached and this wire is passed through an opening in the section 5 and welded or connected to a terminal plate 26 that is secured by a terminal screw 27 to the body ofthe plug.

This plate is provided with a resilient or spring blade 28 that forms part of the usual lamp switch, of which the key is indicated as 29 and the pivot pin is 30. The pin extends transversely through the body of the plug and near one end is fashioned with a cam head or connector 31 that is designed, when the key is turned to frictionally engage the blade 28 and a complementary blade 32 of the switch. In Figure 3 the lamp switch 1s shown turned to open position, but it will be understood that the switch is closed in order that the lamp may automatically be illumined when the fuse link is severed.

The spring blade 32 is of U-shape and is secured in the end of the hollow section 4 by means of a stud 33, which stud also secures the usual contact head 34 to the section and is adapted for frictional and electrical connection with the lamp contact-member on the shell head 2 of the lamp.

The return current from the lamp passes through its shell 2 to the socket shell 3, and thence through a plate 35, and wire 36 to the point 37 where the wire is soldered to the shell 10 of the plug.

The screw or bolt 7, which aids in securin together the three body sections, is employe to secure the bent end of the plate 35 at the end of the section 4, and a screw 38 also secures the plate 35 at the side of the device.

When the fuse link is burned out or severed, the lamp circuit controlled by this plug device is cut oii1 from the main line wires, and the signal lamp 1 only, is illuminated at the fuse plug. The current for the signal lamp passes from the main line through head 13 and thence through the connections along the central interior of the plug device to the lamp, thence out through the shell 3, plate 35, wire 36 and point 37 to the shell 10 and from there through thev shell 4of the socket into which plug 10 is screwed to the negative wire of the main line.

Various changes may be made in the exemplified structure, and the usual necessary accessories, such as a cover or shield 39, are contemplated in the construction of the fuse device for giving` the proper finish to the device, and of course one of these fuse plugs is used at the fuse board for controlling each lighting circuit in a dwelling, or other place to be lighted.

From .the above description taken in connection with my drawings, it will be apparent that the lamp 1 is illuminated as a visible signal to indicate the location of a burned out fuse in a lamp circuit, and the defective plug may readily be replaced by a new one.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is 1. The combination in a fuse plug having an electric lamp and a normally open lamp circuit, a normally closed circuit for the plug including a fuse-link, said plu circuit including a movable Contact mem er operable when the link is severed for closing the lamp circuit when the plug circuit is broken.

2. The combination in a sectional fuse plug having an electrically operated signal lamp mounted in one section, a stationary contact head for the signal lamp mounted in another section, and electrical connections between said head and the lam mounted in an ntermediate section, of a use holder mounted in the second mentioned section, a fuse link, stationary means on the holder for retaining one end of the link and movable means on the holder for retaining the other end of the link, and means for moving the latter means to contact with said head when the link is severed.

In testimony whereof I have aiixed my signature.

THOMAS B. BURNO. 

